Our aerial reconnaissance drones recently sighted http://ec2-23-20-214-191.compute-1.amazonaws.com/8f05e96b3986c333240ab1ecf03a2bb2/ these new robot prototypes but we cannot figure out how to turn them on (INSERT INAPPROPIATE JOKE). Can you help us solve the mystery and get their electrons flowing?
The challenge included pictures of 3 breadboards with random ICs on them and a single LED. The goal was to set the DIP switches on the board to the correct values to light up the LED. We were given 20+ pictures of the boards from different angles to figure out the challenge.
The first step is to identify the chips: We started with Board 3, which contained mostly 7400 series digital logic chips. This is good, they're easy to model out and we're familiar with them!
Board 2 -- more 7400 family.
Board 1 -- a little different...
About that 4048, I found a datasheet that describes it as a "CMOS Multifunction Expandable 8-Input Gate"....what? So, it turns out, the 4048 has 8 inputs, and an additional 3 "binary control" inputs. These 3 inputs Ka, Kb, and Kc change the logic of the entire chip.
Joy...
So, we originally tried going at this on graph paper, but ended up modeling the entire circuit in MultiSim.
The only hiccup with MultiSim is having to model the 4048. That took about 20 minutes and didn't include any of the logic, just the package and footprint pins. Boards 2 and 3 we were able to simulate and get the answers "00111" and "0100" for the dip switches.
Board 1 was a little more difficult. We started to figure out the logic by hand, but eventually gave up after discovering the first two bits had to be '10'. This left 4 bits, which was simple enough to brute force.
The correct combo ended up being: 101001, 00111, 0100. We solved this challenge in the last 90 minutes of the game, putting us into 3rd place.
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